Experimental evidence was presented for structural transformation of multiply twinned CuAu nanoparticles to single-crystalline morphology by 0.5keV helium irradiation. This finding was unexpected as the stability of twin boundaries should not be affected by ion-beam–induced Frenkel pairs. Molecular-dynamics simulations reveal, however, a new transformation mechanism based upon transient amorphization of the particle. By comparing with irradiation simulations of elemental nanoparticles, as well as alloyed bulk samples and surface cascades, it was shown that this transformation route was only present in alloyed particles. Moreover, the observed amorphization was more efficient for twinned than single-crystalline particles. This, together with the fast recrystallization kinetics in CuAu, explained the experimentally observed untwinning process.

From Multiply Twinned to FCC Nanoparticles via Irradiation-Induced Transient Amorphization. T.T.Järvi, D.Pohl, K.Albe, B.Rellinghaus, L.Schultz, J.Fassbender, A.Kuronen, K.Nordlund: EPL, 2009, 85[2], 26001 (6pp)